The present invention concerns a method for the manufacturing of bevel gears, in particular a method for bevel gear milling and bevel gear grinding.
FIG. 1 shows a known method for manufacturing bevel gears with a one-tooth milling cutter. With this method, the milling tooth simultaneously cuts two tooth flanks. The gear or the milling head then rotates by an angle xcex1 equal to the pitch between the points of contact of two successive teeth and the next two tooth flanks are cut.
Although this method is fast, it does not guarantee a good quality of the bearing surface. The bevel gears manufactured according to this method are therefore noisy and hardly efficient.
It has therefore been proposed to mill each tooth flank individually with a modified tool. A corresponding known method generating the correct tooth profile both at the outside diameter as well as at the inside diameter is illustrated in FIGS. 2 and 3.
This method uses two tools or a tool 2 with two cutting teeth. The first tool (respectively the tool""s first tooth) mills the left tooth flank whilst the right tooth flank is milled by the second tool resp. tool tooth. Along the contact path, all the tooth flanks are cut one after the other. With this method, bevel gears of small and large size pitch have already been manufactured.
This method can only be used with special milling machines allowing an inclination xcex40 of the axis of the gear cutter. Such machines are however slow, expensive and complicated.
DE-C 104 582 describes another method for machining spur toothed bevel gears, wherein the tooth flanks are milled with a disc milling cutter. The left tooth flanks are milled at a different time than the right tooth flanks; the bevel gear is rotated between the milling process of the left tooth flank and the milling process of the right tooth flank.
Although this method allows a high production rate, it is not possible with this form cutter to generate all theoretical involutes between the outside and the inside bevel gear diameter. The quality of the bearing surface of the bevel gears manufactured with this machine is thus insufficient for high standards.
Another method for generating bevel gears with crowned tooth flanks has been described in patent DE-C1-4122459.
It is therefore an aim of this invention to propose a new and improved bevel gear manufacturing method, in particular a new and improved bevel gear milling method and bevel gear grinding method.
It is another aim of this invention to propose a new bevel gear milling method that can also be used with inexpensive milling machines with which the axis of the gear cutter cannot be inclined.
It is another aim of this invention to propose a new bevel gear milling method that is faster than the known methods without impairing the quality of the bearing surface.
It is another aim of this invention to propose new tools for carrying out the method, in particular new milling heads, new grinding discs and new control programs.
According to the present invention, these aims are achieved in particular through the characteristics of the independent claims. Further advantageous embodiments are moreover described in the dependent claims and in the description.
In particular, these aims are achieved in that each tooth flank is milled individually with a disc milling cutter. Each tooth flank is milled following the path of contact and accurately in the center. The gear tooth base has the same depth along the pitch circle. In-between the milling process of at least a left tooth flank and the milling process of at least a right tooth flank, the machined bevel gear is rotated by an angle that is not a multiple of the pitch xcex1 between the points of contact of two successive teeth (base pitch). The inclination of the axis of the disc milling cutter remains unchanged during the milling process of said gear.
An advantage of the present invention is that it is possible to load a CNC machine automatically so that multiple-machine operation is possible.
Another advantage of the invention is that a high production rate can be achieved and that the disc milling cutters have a long service life.
Another advantage of the invention is that the most cost-effective tooth length can be chosen.
Another advantage of the invention is that the tooth bearing can be corrected in length crowning and in depth crowning in order to achieve the most cost-effective running characteristics.